Monitoring COTS display devices for HWD/HUD/EVS via transparent photodetectors and imagers

ABSTRACT

Systems and a related method for monitoring commercial off the shelf (COTS) display devices in an avionics display system ensure that the COTS display devices are compliant with hazard classifications by positioning transparent photodetectors in the optical path to monitor the images and components generated and projected by the COTS display devices. Transparent photodetectors are positioned downstream in the optical path to monitor image orientation, refresh rate, or brightness of displayed images and image elements. The system may include transparent image sensors for capturing scene content and monitoring image integrity by comparing the captured scene content to the displayed images. Transparent image sensors positioned proximate to camera cores of an enhanced vision system (EVS) may verify the alignment of individual component image streams combined into an image stream displayed via HDD, HUD, HWD, or a like display element.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. patent application Ser. No.14/814,020, filed on Jul. 30, 2015. Said U.S. patent application Ser.No. 14/814,020 is herein incorporated in its entirety.

BACKGROUND

Avionics display systems such as head-worn displays (HWD), head-updisplays (HUD), and enhanced vision (EV) systems (EVS) may employcommercial off-the-shelf (COTS) display devices to reduce the high costof custom display devices. However, the use of COTS devices lackingDO-254 design assurance may not provide sufficient integrity to maintaincompliance with aviation hazard classifications. The conventionalsolution is the use of multiple independent monitoring schemes. Forexample, a HUD utilizing one or more COTS display devices may employ afirst monitor to ensure that the display is not stuck, flipped, orotherwise generating a hazardously misleading image. A second monitormay ensure that a sudden “all white all bright” (AWAB) condition (orsimilar shift in brightness) will not incapacitate the pilot. Stillanother monitor may be employed to ensure that display graphicsgenerators have not mispositioned or misaligned critical symbologymerged to the displayed images. Historically, each of these variousmonitoring systems have been separately implemented using widely variedand complex methods.

If the HUDs and head-worn devices (HWD) of the future are to handle CAT3 landing credit and low visibility operations (e.g., either with nodecision height or a decision height lower than 100 feet (30 m) and arunway visual range not less than 700 feet (200 m)), size, weight,power, and cost (SWaP-C) considerations may mandate the use of COTSdevices as opposed to expensive custom engineered displays.Consequently, similar mechanisms of display path monitoring may berequired. EV systems, which employ complex COTS devices, provideadditional challenges in camera core monitoring. For example, an EVS mayhave several independent camera cores, produced by a variety of vendorsand each providing different scene content. Each core must be shown notto present a critically misaligned or misleading image, or the combinedvision stream uniting the feeds of different camera cores may present ahazardously incoherent image. Conventional solutions, which involvematching dead pixels in the output images to known locations, are havingtrouble keeping up with the continually improving quality of EV systems.

SUMMARY

In one aspect, embodiments of the inventive concepts disclosed hereinare directed to a system for monitoring the image integrity of COTSdisplay modules in a HUD or HWD avionics display system. The system mayinclude an image source for generating image streams displayed by theHUD/HWD. The system may include a graphics processor for generatingsymbology relative to the displayed images and merging the symbologyinto the image stream. The system may include collimating opticsdefining an optical path from the COTS display module to the displayelement or surface of the HUD/HWD. The system may include one or moretransparent photodetectors or image sensors positioned in the opticalpath for capturing the generated image stream. The system may include aprocessor connected to the photodetectors for monitoring the brightness,orientation, or refresh rate of the generated image stream to bedisplayed by the display element.

In a further aspect, embodiments of the inventive concepts disclosedherein are directed to a system for monitoring the image integrity ofCOTS display modules in an EVS. The system may include a series of COTScamera cores, each core detecting EM radiation in specific spectralbands and each camera core generating a band-specific image streamassociated with the detected EM radiation. The system may includedisplay electronics for generating a combined image stream formed bycombining the image streams generated by the camera cores and displayingthe combined image stream via a HDD, HUD, HWD, or other display element.The system may include a series of transparent image sensors, each imagesensor positioned proximate to a camera core for generating an imagestream specific to the spectral bands of the corresponding camera core.The system may include a processing monitor connected to the transparentimage sensors for generating control image streams and evaluating thealignment of the combined image stream by comparing the control imagestreams to the image streams generated by the transparent image sensors.

In a still further aspect, embodiments of the inventive conceptsdisclosed herein are directed to a method for monitoring COTS displaydevices in a HUD, HWD, EVS, or other avionics display system. The methodmay include generating an image stream via an image source. The methodmay include transmitting the generated image stream to a COTS displaymodule via an optical path defined by collimating optics. The method mayinclude detecting the generated image stream via transparentphotodetectors or image sensors positioned in the optical path. Themethod may include evaluating the orientation, refresh rate, orbrightness of the display unit via a monitor connected to thephotodetectors or image sensors. The method may include displaying thegenerated image stream via a display element of the system.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations of the inventive concepts disclosed herein may be betterunderstood when consideration is given to the following detaileddescription thereof. Such description makes reference to the includeddrawings, which are not necessarily to scale, and in which some featuresmay be exaggerated and some features may be omitted or may berepresented schematically in the interest of clarity. Like referencenumerals in the drawings may represent and refer to the same or similarelement, feature, or function. In the drawings:

FIG. 1 illustrates of an exemplary embodiment of a system for monitoringCOTS devices according to the inventive concepts disclosed herein;

FIGS. 2A and 2B illustrate exemplary embodiments of transparentphotodetectors, and FIG. 2C an exemplary embodiment of a transparentimage sensor, of the system of FIG. 1;

FIG. 3 illustrates an exemplary embodiment of a head-worn device (HWD)of the system of FIG. 1;

FIG. 4 illustrates an exemplary embodiment of an enhanced vision system(EVS) according to the inventive concepts disclosed herein; and

FIG. 5 illustrates an exemplary embodiment of a method for monitoringCOTS display devices according to the inventive concepts disclosedherein.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Before explaining at least one embodiment of the inventive conceptsdisclosed herein in detail, it is to be understood that the inventiveconcepts are not limited in their application to the details ofconstruction and the arrangement of the components or steps ormethodologies set forth in the following description or illustrated inthe drawings. In the following detailed description of embodiments ofthe instant inventive concepts, numerous specific details are set forthin order to provide a more thorough understanding of the inventiveconcepts. However, it will be apparent to one of ordinary skill in theart having the benefit of the instant disclosure that the inventiveconcepts disclosed herein may be practiced without these specificdetails. In other instances, well-known features may not be described indetail to avoid unnecessarily complicating the instant disclosure. Theinventive concepts disclosed herein are capable of other embodiments orof being practiced or carried out in various ways. Also, it is to beunderstood that the phraseology and terminology employed herein is forthe purpose of description and should not be regarded as limiting.

As used herein a letter following a reference numeral is intended toreference an embodiment of the feature or element that may be similar,but not necessarily identical, to a previously described element orfeature bearing the same reference numeral (e.g., 1, 1 a, 1 b). Suchshorthand notations are used for purposes of convenience only, andshould not be construed to limit the inventive concepts disclosed hereinin any way unless expressly stated to the contrary.

Further, unless expressly stated to the contrary, “or” refers to aninclusive or and not to an exclusive or. For example, a condition A or Bis satisfied by anyone of the following: A is true (or present) and B isfalse (or not present), A is false (or not present) and B is true (orpresent), and both A and B are true (or present).

In addition, use of the “a” or “an” are employed to describe elementsand components of embodiments of the instant inventive concepts. This isdone merely for convenience and to give a general sense of the inventiveconcepts, and “a’ and “an” are intended to include one or at least oneand the singular also includes the plural unless it is obvious that itis meant otherwise.

Finally, as used herein any reference to “one embodiment,” or “someembodiments” means that a particular element, feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the inventive concepts disclosed herein.The appearances of the phrase “in some embodiments” in various places inthe specification are not necessarily all referring to the sameembodiment, and embodiments of the inventive concepts disclosed mayinclude one or more of the features expressly described or inherentlypresent herein, or any combination or sub-combination of two or moresuch features, along with any other features which may not necessarilybe expressly described or inherently present in the instant disclosure.

Broadly, embodiments of the inventive concepts disclosed herein aredirected to systems and related methods for monitoring COTS displaydevices in an avionics display system, whether that display system is aHUD, HWD, or EVS-based system. The cost of custom-engineered displaydevices utilizing COTS components may be reduced by providing built-inassurance of the image integrity via low size, weight, power, and cost(SWaP-C) devices. Embodiments of the inventive concepts disclosed hereinmay maintain the hazard compliance of cost-effective COTS displaydevices via the use of transparent photosensing technology, which may becompact enough to scale down to HUD and HWD applications yetsufficiently robust to monitor display devices of continually advancingquality, including multi-stream/multi-band EVS or CVS systems.

Referring to FIG. 1, an exemplary embodiment of an avionics displaysystem 100 for may include an image source (image processor) 102, agraphics processor 104 (e.g., synthetic vision system (SVS)), one ormore COTS display modules 106 such as a light-emitting diode (LED)illuminator or liquid crystal on silicon (LCoS) projector; andcollimating optics 108 defining an optical path 108 a from the displaymodule 106 to a combiner 110 or other surface of a display element(e.g., a HWD microdisplay surface). The image source 102 may beconnected to one or more externally mounted sensors for detecting EMradiation in, e.g., the visible, infrared (IR), or near-infrared (NIR)spectral bands. The image source 102 may then generate, based on thesensed EM radiation, images for display by the avionics display system100, the display element of which may be a HUD or a HWD configured forspecific pilot or crewmember. The avionics display system 100 may be acombined vision system (CVS) in which the symbology is generated by thegraphics processor 104 (e.g., an aircraft horizon line or flight pathvector) and merged into the output of the image source 102 to generate acombined image stream 112 for display by the HUD/HWD. The optical path108 a (optical chain) may be defined by collimating optics 108connecting the display module 106 to the combiner 110.

The avionics display system 100 may monitor the COTS display module 106(or one or more aspects of the combined image stream 112 displayedthereby) via transparent photodetectors 114 placed within the opticalpath 108 a. It is contemplated that the transparent photodetectors 114may be optimally positioned downstream in the optical path 108 a (i.e.,proximate to the combiner 110 or display surface), or beyond any pointin the optical path wherein design failure could corrupt or adverselyaffect the integrity of the image stream 112 (or of any symbologyincluded therein). The transparent photodetectors 114 allow detection orsensing of light within the optical path 108 a without obscuring thecombined image stream 112 presented to the pilot via the combiner 110.The transparent photodetectors 114 may include photodiodes orwavelength-specific materials for capturing image detail (e.g., a “dark”portion of the combined image stream 112 not associated with criticalcontent) associated with a particular spectral band (for, e.g.,visible-band, IR, or NIR imaging).

For example, the transparent photodetector 114 may be a singletransparent camera or image sensor capable of detecting multiplegeometric or wavelength specific features (e.g., image brightness, imageorientation, image refresh rate, symbol positioning) and comparing thosefeatures to independently computed control features generated by anindependent processing resource 116 connected to the transparent cameraor image sensor. In some implementations, the system 100 may monitor theintegrity of the displayed image via, e.g., an infrared (IR) ornear-infrared (NIR) LED 106 a or similar illuminator or emitter, theilluminator output specific to one or more wavelengths or spectral bandsinvisible to the pilot but detectable by the transparent photodetectors114, combined with time phasing. For example, the processing resource116 may provide phased processing for the generation, detection andconfirmation of display refresh patterns. The NIR LED 106 a may bepositioned in the optical path 108 a but outside the primary (e.g.,visible-band) illumination path, using a predetermined imager pattern orarea of the combiner 110 or display surface to test for imagemisalignment or refresh rate issues.

The avionics display system 100 may include one or more monitorprocessors 116 linked to the transparent photodetectors 114 forverifying specific display aspects of the COTS display devices 106 andthe image stream 112 generated thereby. For example, an all white/allbright (AWAB) monitor (116 a) may monitor the brightness of the combinedimage stream 112 to ensure that the pilot is not disoriented orincapacitated by sudden shifts in luminous intensity. An orientationmonitor (116 b) may verify that the combined image stream 112 (or anysymbology integrated therein) is neither “flipped”, e.g., presenting aninverted image stream, nor “stuck”, e.g., improperly or insufficientlyrefreshing the displayed image stream, nor misaligned, e.g., withrespect to multiple image streams portraying similar or identical scenecontent as viewed through different spectral bands. The presence of anyone of these conditions could result in a hazardously misleading image.

Referring to FIGS. 2A through 2C, several exemplary embodiments of thetransparent photodetector 114 of the avionics display system 100 of FIG.1 are shown. By way of a non-limiting example, the avionics displaysystem 100 may incorporate multiple variations of transparentphotodetectors 114 a-b or transparent image sensors 114 c depending onSWaP-C considerations or robustness requirements. Referring specificallyto FIG. 2A, a transparent photodetector 114 a may incorporate awavelength-sensitive layer 120 comprising a photosensitive dye ormaterial (e.g., a layer of cyanine dye capable of absorbing NIRradiation). For example, the avionics display system 100 may include anemissive display system incorporating multiple emissive devices ororganic light-emitting diodes (OLED), wherein the wavelength-sensitivelayer 120 is sandwiched between anode/hole transport layers (122) andcathode/electron transport layers (124) fixed to an electricallyconductive glass substrate 126.

Referring specifically to FIG. 2B, a transparent photodetector 114 b maybe implemented and may function similarly to the transparentphotodetector 114 a of FIG. 2A, except that the transparentphotodetector 114 b may include a nanolayer 128 sandwiched between twoconductive glass substrates 126 a, 126 b. The transparent photodetectormay alternatively incorporate substrates of polymer film or anysimilarly appropriate material. The nanolayer may include photosensitivecarbon nanotubes, thin-film tungsten disulfide (WS₂) nanoparticles,quantum dots, or other similar nanoscaled photosensitive materials.

Referring specifically to FIG. 2C, a transparent image sensor 114 c maybe implemented and may function similarly to the transparentphotodetector 114 b of FIG. 2B, except that the transparent image sensor114 c may include a luminescent concentrator (LC) 132 as an interiorlayer or sandwiched between transparent substrates. For example, the LC132 may include a layer of transparent polymer film incorporatingphotodiodes or fluorescent/wavelength-specific particles configured tocapture incoming light of a specific wavelength and, e.g., re-emit thecaptured light at a slightly different wavelength. This captured andre-emitted light may be conducted through the LC layer to arrays ofoptical sensors 134 positioned around the outer edges of the transparentimage sensor 114 c. The processing resource 116 (FIG. 1) may collectinformation from the optical sensors 134 to determine, for example, atwhich precise points light strikes the surface of the LC 132, andthereby reconstruct the image stream 112 passing through the transparentimage sensor 114 c.

Referring to FIG. 3, a compact microcollimator 108 b may be implementedand may function similarly to the collimating optics 108 of FIG. 1,except that the compact microcollimator 108 b may be implemented in aHWD wearable by a pilot or crewmember as a helmet or goggles, or in afixed HUD. The compact microcollimator 108 b may incorporate amicrodisplay surface 110 a proximate to the pilot's eye to which theimage stream 112 may be directed from the display module 106. Thecompact microcollimator 108 b may include one or more transparentphotodetectors 114 positioned proximate to the projecting waveguide 136terminating the optical path 108 a. The compact microcollimator 108 bmay handle process monitoring of the transparent photodetectors 114 viaan embedded or reduced instruction set computing (RISC) processor, or aprocessor 116 d wirelessly linked to the compact microcollimator 108 b.

Referring to FIG. 4, an enhanced vision system (EVS) 100 a may beimplemented and may function similarly to the system 100 of FIG. 1,except that the EVS 100 b may combine, via display electronics 138,multiple visual channels (image streams 112 a-c) into a comprehensivevisual stream 140 for display (by, e.g., a HDD 142, a HUD 144, or a HWD146). For example, the comprehensive visual stream 140 may represent asingular field of view (FoV) as rendered in varied spectral bands,whereby each individual image stream 112 a-c presents distinct scenecontent corresponding to the FoV. The individual image streams 112 a-cmust be precisely aligned or the comprehensive visual stream 140 maypresent a hazardously misleading or incoherent image. The EVS 100 b mayinclude multiple camera cores 148, 150, 152; even within a single EVSeach camera core may be produced by a different vendor and wouldotherwise require a distinct and complex conventional monitoringsolution.

In addition to the orientation, refresh, brightness, and symbologymonitoring discussed above, a particular challenge with respect tomonitoring the alignment of COTS camera cores 148, 150, 152 of the EVS100 b is the lack of a known image or image characteristic with which tocompare the camera core output (image streams 112 a-c). The EVS 100 bmay address this challenge by positioning a transparent image sensor 114c in line with each camera core 148, 150, 152 to capture relevant scenecontent (112 d-f) similar to the image streams 112 a-c generated by eachcamera core. The processing monitor 116 may then compare thecharacteristics of each individual image stream 112 a-c with itsindependently captured scene-content counterpart 112 d-f to verify imagestream alignment.

Referring now to FIG. 5, an exemplary embodiment of a method 200 formonitoring COTS display devices according to the inventive conceptsdisclosed herein may be implemented by the avionics display system 100,and may include one or more of the following steps. At a step 202, animage source or camera core of the system generates an image stream fordisplay. The image stream may be a combined image stream includingsymbology generated by a graphics processor or SVS of the system andmerged into the image stream. The system may be an EVS wherein multipleimage streams are generated by multiple camera cores of the EVS, eachimage stream associated with one or more particular spectral bands.

At a step 204, the generated image stream is transmitted by a COTSdisplay module through an optical path defined by collimating optics toa combiner or display element.

At a step 206, the generated image stream is detected via transparentphotodetectors positioned in the optical path. The system may includetransparent image sensors positioned in the optical path, configured togenerate scene content or secondary images for verifying the integrityof the generated image stream. The system may detect wavelength-specificimagery associated with one or more nonvisible bands (e.g., NIR)generated by wavelength-specific image sources via wavelength-specifictransparent photodetectors positioned in the optical path.

At a step 208, aspects of the display module are evaluated based on thedetected image stream via a processing monitor connected to thetransparent photodetector. The processing monitor may compare thedetected image stream to the scene content or secondary images generatedby the transparent image sensors.

At a step 210, the generated image stream is displayed via the combineror display surface. The generated image stream may be displayed by aHDD, a HUD, or a HWD.

As will be appreciated from the above, systems and methods according toembodiments of the inventive concepts disclosed herein may enable theuse of low-SWaP-C COTS display devices in avionics display systems (asopposed to high-cost custom-designed devices) by providing a similarlylow-SWaP-C means of monitoring the COTS display devices and ensuringthat the COTS display devices are compliant with aviation hazardclassifications.

It is to be understood that embodiments of the methods according to theinventive concepts disclosed herein may include one or more of the stepsdescribed herein. Further, such steps may be carried out in any desiredorder and two or more of the steps may be carried out simultaneouslywith one another. Two or more of the steps disclosed herein may becombined in a single step, and in some embodiments, one or more of thesteps may be carried out as two or more sub-steps. Further, other stepsor sub-steps may be carried out in addition to, or as substitutes to oneor more of the steps disclosed herein.

From the above description, it is clear that the inventive conceptsdisclosed herein are well adapted to carry out the objectives and toattain the advantages mentioned herein as well as those inherent in theinventive concepts disclosed herein. While presently preferredembodiments of the inventive concepts disclosed herein have beendescribed for purposes of this disclosure, it will be understood thatnumerous changes may be made which will readily suggest themselves tothose skilled in the art and which are accomplished within the broadscope and coverage of the inventive concepts disclosed and claimedherein.

We claim:
 1. A system for monitoring display devices in an avionicsdisplay system, comprising: at least one image source configured togenerate at least one image stream; at least one graphics processorconfigured to generate at least one symbol for merging with the at leastone image stream; at least one display element configured to display theat least one image stream; collimating optics defining an optical pathof the at least one image stream from the at least one image source tothe at least one display element; at least one transparent photodetectorpositioned in the optical path proximate to the display element,disposed between the display element and a user, the transparentphotodetector configured to detect one or more first control featuresassociated with the at least one image stream; and at least one monitorprocessor coupled to the transparent photodetector and to the imagesource, the at least one processor configured to: generate one or moresecond control features associated with the at least one image stream;and monitor the at least one display element by comparing the one ormore first control features to the one or more second control features.2. The system of claim 1, wherein the one or more first control featuresand the one or more second control features include at least one of: abrightness level; a refresh rate; an image orientation; a wavelengthspecific feature; an all white all bright (AWAB) condition; and apositioning of the at least one symbol.
 3. The system of claim 1,wherein: the at least one image source includes at least onewavelength-specific image source positioned in the optical pathproximate to the transparent photodetector; and the at least one imagestream includes at least one image corresponding to one or morenonvisible spectral bands.
 4. The system of claim 2, wherein the atleast one monitor processor includes a phased processor configured tomonitor the at least one refresh rate by generating at least one refreshpattern.
 5. The system of claim 1, wherein: the at least one displayelement includes at least one emissive display comprising at least adisplay surface and a plurality of emissive devices; and the at leastone transparent photodetector is positioned between the display surfaceand at least one emissive device of the plurality of emissive devices.6. The system of claim 1, wherein: the at least one transparentphotodetector includes one or more photosensitive materials fixedbetween a first substrate and a second substrate, the one or morephotosensitive materials include at least one of a nanotube, aluminescent concentrator, a fluorescent particle, a photosensitive dye,and a quantum dot; and one or more of the first substrate and the secondsubstrate is fashioned of at least one of conductive glass and polymerfilm.
 7. The system of claim 1, wherein the system is embodied in atleast one of a head-up display (HUD) system and a head-worn display(HWD) system.
 8. The system of claim 7, wherein the at least one monitorprocessor includes at least one of: an embedded processor; and aprocessor wirelessly linked to at least one of the HUD system and theHWD system.
 9. A system for monitoring display devices in an enhancedvision system (EVS), comprising: two or more camera cores, each cameracore coupled to one or more electromagnetic (EM) sensors configured todetect EM radiation in one or more EM spectral bands, each camera coreconfigured to generate a component image stream associated with the oneor more EM spectral bands; at least one transparent image sensorpositioned proximate to each camera core, disposed between the cameracore and a user, each transparent image sensor configured to capturefirst image content associated with the corresponding component imagestream; at least one monitor processor coupled to the at least onetransparent image sensor and to the two or more camera cores, theprocessing monitor processor configured to: capture second image contentassociated with each component image stream; and evaluate an alignmentof the at least one component image stream by comparing the first imagecontent to the corresponding second image; display electronics coupledto the two or more camera cores and configured to generate at least onecombined image stream by combining the two or more component imagestreams; and at least one display element coupled to the displayelectronics, the display element configured to display the at least onecombined image stream.
 10. The system of claim 9, wherein the two ormore camera cores include at least one of: a first camera coreassociated with one or more first aircraft-based EM sensorscorresponding to a first spectral band of the one or more EM spectralbands; and a second camera core associated with one or more secondaircraft-based EM sensors corresponding to a second spectral band of theone or more EM spectral bands.
 11. The system of claim 9, wherein thedisplay element includes at least one of a HUD and a HWD.
 12. A methodfor monitoring display devices of an avionics display system, the methodcomprising: generating at least one first image stream via an imagesource; transmitting the first image stream through an optical path toat least one display element via collimating optics; detecting at leastone first control feature associated with the first image stream via atleast one transparent photodetector positioned in the at least oneoptical path, between the display element and a user; generating atleast one second control feature associated with the first image streamvia at least one monitor processor coupled to the image source;evaluating at least one aspect of the display module by comparing the atleast one first control feature and the at least one second controlfeature via the at least one monitor processor; and displaying the firstimage stream via the at least one display element.
 13. The method ofclaim 12, wherein generating at least one first image stream via animage source includes: generating at least one symbol corresponding tothe first image stream; and merging the at least one first image streamwith the at least one symbol via a graphics processor.
 14. The method ofclaim 12, wherein evaluating at least one aspect of the display modulebased on the detected image via at least one processor coupled to thetransparent photodetector includes: detecting at least one first controlfeature associated with the first image stream via at least onetransparent photodetector positioned in the at least one optical pathincludes detecting at least one of a first brightness level, a firstrefresh rate, a first image orientation, a first wavelength specificfeature, and a first symbol positioning via at least one processorcoupled to the transparent photodetector; and generating at least onesecond control feature associated with the first image stream via atleast one monitor processor coupled to the image source includesgenerating at least one of a second brightness level, a second refreshrate, a second image orientation, a second wavelength specific feature,and a second symbol positioning via the at least one monitor processor.15. The method of claim 12, wherein displaying the first image streamvia the at least one display element includes: displaying the firstimage stream via at least one of a head-up display (HUD) and a head-worndisplay (HWD).
 16. The method of claim 12, wherein the at least onefirst image stream is a first component image stream of two or morecomponent image streams of a combined image stream, each component imagestream associated with one or more electromagnetic (EM) spectral bands.17. The method of claim 16, wherein: detecting at least one firstcontrol feature associated with the first image stream via at least onetransparent photodetector positioned in the at least one optical pathincludes 1) detecting first image content associated with the firstcomponent image stream and 2) detecting second image content associatedwith at least one second component image stream; and evaluating at leastone aspect of the display module by comparing the at least one firstcontrol feature and the at least one second control feature via the atleast one monitor processor includes evaluating an alignment of at leastone of the first component image stream and the at least one secondcomponent image stream by comparing the at least one second controlfeature to one or more of the corresponding first image content and thecorresponding second image content.
 18. The method of claim 15, whereindisplaying the first image stream via the at least one display elementincludes: displaying the combined image stream via the at least onedisplay element.